Method of detecting washouts in rotary well drill strings



y 1942- J. T. HAYWARD 2,290,179v

METHOD OF DETECTING WASHOUTS IN ROTARY WELL DRILL STRINGS Original FiledMarch 4, 1939 FIG. 1

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i 2 v ENVENTOR JoH/v 7. HAYWARD ATTORNEY Patented July 21, 1942 UNITEDSTATES METHOD OF DETECTING WASHOUTS IN ROTARY WELL DRILL STRINGS John T.Hayward, Tulsa, Okla,

Original application March 4, 1939, Serial No. 259,849. Divided and thisapplication October 2, 1939, Serial No. 297,475

10 Claims.

This application is a division of my co-pending application Serial No.259,849, filed March 4, 1939.

This invention relates to a method and apparatus for measuring the rateof flow of drilling fluids through a well during the drilling thereof,and for detecting and measuring the change in rate of flow of suchdrilling fluids.

In the ordinary course of drilling a well, such as an oil or gas well,by the rotary method, a hydraulic fluid, such as a mud fluid consistingordinarily of a suspension of clay or earthy solids in water, is forceddown through a string of hollow drill pipe to the bottom of the well,where it is discharged from the drill pipe through two holes in the bit,commonly known as the eyes, thence upwardly through the annular spacebetween the drill pipe and the wall of the well bore to the surface ofthe ground.

Accurate and continuous knowledge of the volume and rate of flow of thestream of mud fluid through the well is of great importance to thedriller in many operations and is particularly important in connectionwith a continuous coring or logging method such as described in detailin my former application, Patent 2,214,674 of Sept. 10, 1940. Anotherimportant application is in the detection of "wash-outs in the drillpipe.

Heretofore, no satisfactory method or apparatus has been devised foraccurately and continuously measuring the volume and rate of flow of amud fluid through a well. Because of the unusual and varyingcharacteristics of such fluids, which are very abrasive in character,and vary very widely in their viscosity and densities during thedrilling operation, all meters which have attempted to be applied tometering of such fluids have been rendered totally inaccurate andundependable in their measurements and none have been designed, as yet,which would accurately and continuously meter the volume or rate of flowof such drilling fluids through a well.

The present invention provides a new and successful method and apparatuswhich is particularly applicable for measuring the volume and rate offlow of mud fluids through a well during the drilling thereof, and inaddition, simultaneously provides a novel and highly successful methodand apparatus for detecting impending wash-outs in the drill pipe bydetecting the change in rate of flow of the drilling fluid through thewell.

The present application is a division of my application 259,849 filedMarch 4, 1939.

With reference to wash-outs, it should be noted that the so-called eyesof a drilling bit are ordinarily about three-quarters or seveneighths ofan inch in diameter and because of their relatively restricted openingsand the friction in the drill pipe, considerable pressure, gen erally inexcess of 100 pounds per thousand feet of drill pipe, is required tocause the mud fluid to circulate through the well. Since strings ofdrill pipe up to 10,000 feet or more in length are employed in manycases of well drilling, pressures of several hundred pounds to wellabove one thousand pounds may be required. Under such high pressures,should a crack or pin hole be present or develop in the wall of thedrill pipe, or should there be a slight leak in any of the threadedconnections between the sections of drill pipe, the mud fluid will beforced through such defective spots and by its abrasive action under thehigh pressure, will very rapidly enlarge the opening until so much ofthe pipe metal is eroded away that the pipe is severed or parts of itsown weight at the point of erosion. This condition is commonly referredto as a wash-out and results in the loss of the lower portion of thedrilling string in the well requiring a so-called fishingjob to recoverthis portion from the well. Fishing jobs are expensive, time-consuming,and in extreme cases may even cause loss of the well or at least mayrequire that the well be side- 30 tracked past the unrecovered pipe andredrilled *for a substantial portion of its depth. About ninety percentof all fishing jobs in rotary drilling are the result of wash-outs, andit will be evident, therefore, that any method which will warn againstsuch wash-outs before they have progressed to the point of disruption ofthe drilling pipe will be of great value to the industry.

It will be obvious that, as compared with two three-quarters orseven-eighths inch holes at the bottom of the string of drill pipe, anysmall opening in some upper portion of the drill pipe will cause anincrease in the rate of mud circulation. It has been discovered that awash-out is always preceded by a steady but slow increase in the flowrate-usually extending over two to four hours before the pipe fails. Thepumps commonly used on rotary rigs for circulating the mud fluid areordinarily direct-acting pumps and are more-or-less constant pressuredevices which tend to maintain the discharge pressure by speeding-upwhenever the total resistance against their delivery is decreased. Ithas been found, therefore, that by providing suitable means for quicklydetecting increases in the rate of such 55 pumps, impending wash-outsmay be readily detected at their inception, and the drilling thereuponstopped and the defective pipe withdrawn before the complete failure ofthe drill pipe with its attendant fishing iob occurs. At the same timethe novel apparatus employed for detecting wash-outs also functions veryefilciently for measuring continuously the rate and volume of flow ofthe mud fluid through a drilling well, as will be described more fullyhereinafter.

As ordinarily connected in a rotary rig, the mud circulation pumps areout of sight of the driller, and in any case, the rate of increase oftheir speeds is generally so slow before a com plete wash-out occurs,that it will ordinarily escape the attention even of an observerstationed at the pumps.

It is, therefore, a principal object of this invention to provide anovel method for measuring the rate and volume of fiow of mud fluidthrough a well.

Another important object is to provide a novel method for detectingincipient wash-outs in drill pipe by observing the change in the rate offiow of mud fluid through a drilling well.

A more specific object is to provide a method for detecting wash-outs ofdrill pipe by measuring the speed rate at which a constant pressurepumpcirculates mud fluid through a drill pipe, and detecting andmeasuring the change in rate of the pump.

Another object is to provide an apparatus suitable for detecting changesin rate of operation of pumps employed in circulating drilling fluidsthrough wells, whereby the rate and volume of flow of mud fluid througha well may be measured and incipientwash-outs quickly detected.

Other and more specific objects of this invention will become apparentfrom the following description taken in conjunction with theaccompanying drawing which illustrates a form of apparatus particularlyadapted for successfully accomplishing the aforementioned and other ob-Jects of this invention.

In the drawing:

Fig. 1 illustrates an arrangement suitable for accomplishing thepurposes and objects of this invention.

Fig. 2 is a schematic drawing of electrical ap paratus used inconnection with the apparatus of Fi 1.

Referring to the drawing, Fig. 1 shows a well I in which is inserted astring of hollow drill pipe 2 such as is ordinarily employed in rotarydrilling for turning a bit I connected to the 05wer end thereof andprovided with conventional openings or eyes I. A pump 5 has itsdischarge pipe 6 connected to the usual rotary hose I, which is attachedby means of a swivel 8 to the upper end of drill pipe 2. Pump 5 is ofthe wellknown direct-acting type which operates at more-or-less constantpressure which is maintained against reduced resistance in the stream offluid being pumped by the speeding-up of the pump. The pump isconveniently driven by steam which is usually suppliedat a constantpressure and at a volume sufficient to maintain a constant dischargepressure on the pump. While pump 5 is illustrated as a simplex, orsingle cylinder pump, it may be and usually is a duplex type pump. Pump5 has the usual rocker arm 9, which is suitably connected at its upperend to oscillate about a bearing l0 and has its lower end rotativelyseated in the usual cross head II, which is fixedly mounted on thepiston rod l2 in the usual manner. The rest of the pump valve gearconventionally attached to and operated by pump rocker arms, such asrocker arm 9, is not shown. Attached to the upper end of rocker arm 9 isa fixed switch terminal I! which oscillates with the movement of therocker arm and, during a portion of the oscillatory arc, makes contactwith a switch point 14. Switch terminal I; and switch point l4 are sopositioned relative to each other that they make contact with each otherduring a portion of each cycle of the pump piston. Switch terminal I3and switch point ll are connected by wire leads l5 and I6, respectively,to an electrical rate meter, indicated generally at I1, and to anelectrical cycle counter, indicated at l8, both of which will bedescribed in greater detail hereinafter. A suitable source of directcurrent, such as a battery 20, is connected into the circuit in lead IS.The switch which includes switch terminal l3 and switch point it may beof any suitable design which is adapted to open and close during eachcycle of pump 5 so as to permit recording of the pump cycles by ratemeter l1 and counter l8.

Fig. 2 shows the schematic arrangement of the electrical circuitemployed in connection with rate meter l1 and cycle counter l8. Startingat the left hand end of the diagram, we find a battery 20, for which anysuitable source of constant direct current voltage may be substituted.Lead l6 from switch point I next connects into the circuit and lead l5from switch terminal I3 is connected to electrical counter l8, which isof conventional design and adapted to count the total number of cyclesmade up by pump 5, and to a slow-acting relay 25 through respectiveresistors 26 and 21. Relay 25 operates a pair of transfer capacitors2828 which discharge into a measuring circuit which comprises athree-section resistance-capacitance filter 29, each section of which'is provided with its respective condenser 32, and which is in turnconnected to a micro-ammeter, which is preferably provided with twoscales Ila and Nb. Scale Fla is calibrated in stroke cycles per minuteto function as the cycle rate meter for pump I and scale Hb in barrelsper minute, the latter being directly derived from the former bymultiplication thereof by a constant determined from the volumetriccapacity of the pump in barrels per cycle. Scale Ilb will, therefore,give direct readings in barrels per minute. Instead of a single meterhaving two scales, two separate meters, as shown, may be used. Each ofthe scales is provided with a rate indicator hand l9a and lilb,respectively, and one or both with normal index pointers 30a and 30b,respectively, which are adapted to be set manually at any desired pointalong the respective scales Ila and I'll: relative to a predeterminednormal operating-position of the indicator hands lSa and MD.

This circuit operates as follows: Each time the pump 5 operates througha cycle, the switch operated by rocker arm 9 is open and closed. Thecorresponding operation of relay 25 causes one of the transfercapacitors 28 to close on the side toward the voltage source and to becharged fully to the voltage. of the circuit. It is then moved to theother side of the relay contact and discharged into measuring circuit 29down to the voltage on the first filter condenser 32. During this timethe other transfer capacitor 28 is acting similarly, except that itstiming is reversed, and it charges while the first one is discharging,then discharges while the first one is charging again. It can be seenthat the reading of the meter, or meters if two are used, will bedirectely proportional to the voltage supplied from source 20 and willalso be somewhat proportional to the capacitance of the transfercapacitors.

The measuring circuit 29, as indicated, constitutes a filter arrangementto smooth out the pulses of current so as to give a steady reading onthe meters rather than a reading varying through wide limits after eachcondenser discharge. .It is found to be not practical to use a singlesection filter for two reasons. In the first place, the time requiredfor the meters to arrive at steady state readings was excessive, beingof the order of several minutes, and secondly, the remaining amplitudeof current pulses was also excessive for any reasonable amount ofcapacitance and resistance used in the filter. It was found practical touse a three-section filter and thereby attain a satisfactory smoothnessof the reading and also a satisfactory quickness of response inattaining a steady state reading.

The apparatus hereinabove described is employed as follows: Cycle ratemeter I1 is positioned on the drilling rig under the immediateobservation of the driller, usually, whose position in ordinary drillingpractice is remote from the pumps 5. With pump 5 operating at a normalspeed to circulate mud fluid through the well i at the required rate,the normal indicator hands l9a and l9b will reach steady states at somedeflnite positions on scales Ila and Nb, respectively, corresponding tothe normal rate of operation of the pump, as long as no leaks occur inthe drill pipe 2. The normal index pointer 30a is then set in advance ofthis position on scale Ila, for example, at a position marking a 20%increase in the normal speed of the pump. Then, when any leak occurs inthe drill pipe 2, the pump rate will immediately show an increasecorresponding to the rate of leakage of fluid from the drill pipe andthe indicator hand l9a will move toward the position of the normal indexpointer 30a, and will thus immediately indicate to the driller that anincipient wash-out is in progress, and being thus warned, he canimmediately halt the drilling operation and withdraw the drill pipe forreplacement of the pipe section or sections which are found to bedefective. The index pointer 30b may be set, similarly, in advance ofthe normal reading of indicator I9b on scale Nb, and will, of course,function in a similar manner to show change in volume rate of the pump.

Counter l8 will total the number of cycles made by pump 5, and from thenumber of strokes or cycles it records in any given period of time thetotal volume of fluid circulated in that period of time may be readilycalculated by multiplying that number by the volume per cycle factor forthe pump.

Thus it will be evident that this invention discloses 'a novel methodand apparatus for metering the volume and rate of flow of the drillingfluid during the drilling of a well, and for warning against incipientwash-outs of the drill pipe, the method comprising forcing drillingfluid through the drill pipe and the well in a pulsating stream ofpredetermined volume per pulsation, and counting the number ofpulsations to measure the volume of fluid circulated through the well,measuring the number of pulsations per unit of time to determine therate of circulation, and. observing the changes in rate of pulsationunder constant pressure to thereby detect incipient or impendingwash-outs.

Instead of the described electrical cycle rate meter I1, and electricalcounter [8, various forms of mechanical, hydraulic or pneumatic devicesmay be substituted for operation directly or indirectly by the movementof the rocker arm 9 of pump 5.

What I claim and desire to secure by Letters Patent is:

1. In the method of drilling wells wherein a hydraulic fluid iscirculated into and out of a well through a hollow drill pipe by a pumpof fixed volumetric capacity per stroke cycle, the method of detectingincipient wash-outs in said drill pipe which comprises, forcing a streamof said hydraulic fluid through said drill pipe and. said well at apredetermined normal pulsation rate of said pump, and observingincreases in said normal pulsation rate by observing the gradualincreases in the stroke cycle rate of said pump while maintainingsubstantially constant pressure on said stream of fluid to therebydetect incipient washouts.

2. In the method of drilling wells wherein a hydraulic fluid iscirculated into and out of a well through a hollow drill pipe by a pumpof fixed volumetric capacity per stroke cycle, the method of detectingincipent wash-outs in said drill pipe which comprises, forcing a streamof said hydraulic fluid through said drill pipe and said well by saidpump, measuring the stroke rate of said pump and establishing thereby apredetermined normal stroke rate for said pump, continuing themeasurement of the stroke rate of said pump throughout the drillingoperation while maintaining a substantially constant pressure on saidstream of fluid, and observing gradual progressive increase in saidnormal stroke rate of said pump during said drilling operation tothereby detect incipient wash-outs in said drill pipe.

3. In the method of drilling wells wherein a hydraulic fluid iscirculated into and out of a well through a hollow drill pipe by a pumpof fixed volumetric capacity per stroke cycle, the method of detectingincipient wash-outs in said drill pipe which comprises, forcing a streamof said hydraulic fluid through said drill pipe and said well by saidpump, measuring the stroke rate of said pump and establishing thereby apredetermined normal stroke rate for said pump, continuing themeasurement of the stroke rate of said pump throughout the drillingoperation while maintaining substantially constant pressure on saidstream of fluid and continuously comparing the stroke rate of said pumpduring the drilling operation with said normal stroke rate to therebydetect during the drilling operation increases in said stroke rate whichare indications of the incipient wash-outs in said drill pipe.

4. In the method of drilling wells wherein a hydraulic fluid iscirculated into and out of a well through a hollow drill pipe by a pumpof fixed volumetric capacity per stroke cycle, the method of detectingincipient wash outs in said drill pipe developing over extended periodsof time during drilling which comprises, forcing a stream of saidhydraulic fluid through said drill pipe and said well at a predeterminednormal cycle rate by said pump, providing a fixed visual indication ofsaid normal cycle rate, continuously measuring the cycle rate of saidpump throughout the drilling operation while maintaining substantiallyconstant pressure on said stream of fluid, and providing a continuousvisual indication 5. A methodaccording to claim 2 wherein the mechanicalstroke movements of said pump are converted into electrical quantities,and the resulting electrical quantities measured to provide the thereinmentioned rate measurements.

6. In the drilling of wells wherein a hydraulic fluid is circulated intoand out of a well through a hollow drill pipe, the method of detectingincipient wash-outs in said drill pipe which comprises, forcing saidfluid through said drill pipe and said well in a pulsating stream,establishing a predetermined normal pulsation rate therefor,continuously measuring the pulsation rate during the drilling whilemaintaining substantially constant pressure on said stream, andcontinuously comparing the measured pulsation rate with said normalpulsation rate to thereby obtain an indication of gradual increases insaid normal rate which are indicative of incipient wash-outs.

7. In the drilling of wells wherein a hydraulic fluid is circulated intoand out of a well through a hollow drill pipe, the method of detectingincipient wash-outs in said drill pipe which comprises, forcing a streamof drilling fluid through said pipe and said well at a predeterminednormal rate of flow, continuously maintaining constant pressure on saidstream entering said drill pipe, providing an indication of said normalrate, producing a continuous indication of the rate of said fluid whilesaid constant pressure is maintained on said stream, and continuouslycomparing said continuous indication with said indication of said normalrate to thereby detect gradual increases in said normal rate wheerby todetect incipient wash-outs in said drill pipe.

8. In the drilling of wells wherein a hydraulic fluid is circulated intoand out of a well through a hollow drill pipe, the method of detectingincipient wash-outs in said drill pipe which comprises, forcing drillingfluid through said drill pipe and said well in a pulsating stream at apredetermined normal pulsation rate, maintaining constant pressure onsaid stream entering the drill pipe, providing an indication of saidnormal pulsation rate, producing a continuous indication of pulsationrate throughout the drilling operation while said constant pressure ismaintained on said stream, and continuously comparing said continuousindication with said indication of said normal rate to thereby detectincreases in said normal rate whereby to detect incipient washouts insaid drill pipe.

9. In the art of drilling deep wells by the rotary method in which afluid is circulated under a normally maintained pressure down a rotatingdrill stem and upwardly outside thereof, the process of detectingincipient leaks at various points along the drill stem during theregular course of drilling, comprising forcing the fluid down the drillstem, causing a variation in the rate of flow of the fluid attendantupon such an incipient leak, and indicating such variation.

10. In the art of drilling deep wells by the rotary method in which afluid is circulated under a normally maintained pressure down a rotatingdrill stem and upwardly outside thereof, the process of detectingincipient leaks at various points along the drill stern during theregular course of drilling, comprising, forcing a normally pulsatingstream of the fluid down the drill stem, causing an abnormal variationin the pulsation rate of the fluid attendant upon such an incipientleak, and indicating such abnormal variation.

JOHN T. HAYWARD.

